The disclosed invention relates to optical fiber technology and, more particularly, to methods and devices for reducing or eliminating ultraviolet and infrared radiation degradation in a large core polymer fiber (LCP) such that it may be used with available light sources without modification of the light source.
Optical fibers made from polymers are well known. These fibers are typically fabricated from various types of known polymers. These fibers are generally constructed of two major members, an optical polymer core and a cladding member which sheathes the polymer core. LCPs are a variation of polymer optical fibers.
The function of the optical core in an LCP is to transmit light. The transmitted light is typically supplied by a light source from one end of the optical fiber and travels down the fiber to the other end, or escapes from the sides of the optical fiber. The latter type of LCP is referred to as a xe2x80x9cside lightxe2x80x9d fiber, and the former is referred to as an xe2x80x9cend lightxe2x80x9d fiber.
Typically, the polymer cores of LCPs have circular cross sections having diameters that can range between 3 mm to 20 mm. Thus, LCPs can be manufactured with variable thicknesses making them useful in a variety of applications. LCPs are used in architectural applications such as lighting buildings, walkways, stairs and other areas where their functions range from aesthetic enhancement of an area to providing lighting for safety reasons. Generally, LCPs are useful in providing lighting to large areas because of their ease of installation and reasonable cost.
Because the core of LCPs are made from polymer fibers, when in use, LCPs degrade as a result of long term exposure to ultraviolet and infrared radiation emanating from their light sources. Since most light sources used with LCPs produce ultraviolet and infrared radiation, degradation in the polymer core of LCPs is a recurring problem. In some cases, degradation in the polymer core occurs in a matter of weeks after the installation, thus requiring replacement of the LCP.
In cases involving exposure of an LCP""s core to high density ultraviolet or infrared radiation, degradation has been known to occur in a matter of moments. To resolve the problem of ultraviolet or infrared degradation, light sources that do not project ultraviolet or infrared radiation could be used in conjunction with LCPs. This approach is expensive and complicated in that it requires the use of a special technology.
The method herein disclosed takes a different approach to the problem in that instead of modifying the light source, the disclosed method makes it possible to modify the light that emanates from a common light source such that ultraviolet or infrared radiation will not be transmitted to an LCP""s polymer core. Implementation of this approach involves the positioning and placement of a material that does not transmit ultraviolet and infrared radiation, but is optically transparent otherwise, such as a glass rod of a suitable shape and size, between a light source and the core of an LCP.
There are technological obstacles in the implementation of this approach which have to be overcome. Generally, the obstacles to be overcome relate to the proper coupling of an LCP""s core with a glass rod as improper coupling may unduly reduce the efficiency of the light transmitted by the fiber.
The first problem to be overcome relates to light transmission efficiency from a light supplying member being coupled to the LCP""s core. Light energy may be lost at the juncture between the coupling member that is transmitting light to the LCP""s core, and the end of the LCP""s core, if the light receiving end of the core is not properly finished. Coupling may be improper, thus causing inefficient transmission of light, if the cross section of the end of the core of an LCP, where light is received, is not flat and smooth. It is, therefore, imperative that the core""s end be flat prior to coupling.
In addition, successful coupling requires substantial alignment of the members being coupled, and some way of insuring that the two members that are being coupled will not move apart. To keep such members in appropriate alignment, glue as well as mechanical devices conventionally have been used to effect proper coupling.
The methods disclosed herein overcome the above problems by providing steps for modifying an LCP to have a flat and smooth polymer core end, and through the same steps creating a means for receiving and maintaining another member in a substantially aligned position in respect to the end of the core.
A typical LCP is comprised of a polymer core and a cladding covering the same. Generally, the method of this invention involves the removal of a portion of the core of an LCP by heating slowly the LCP from the outside and from all directions at a preselected point along its length, and then stressing the core at a relatively high rate by pulling the core apart sharply. Through carrying out these steps at the appropriate temperatures and at an appropriate stress rate, the core of the LCP will fracture leaving a flat, smooth surface.
In addition, as part of the core is removed, a void is created within the tubular cladding of the LCP. A coupling member such as a glass rod may be then inserted in the void. Such member, if suitable in shape and dimensions, will be snugly received by the LCP that is modified through the methods disclosed herein as fingers of a surgeon are securely received by a surgical glove. As such the member will be positioned in substantial alignment with the end of the LCP core, and clinched in position by the cladding of the LCP upon insertion.
The methods disclosed in this application for the construction of a device to reduce ultraviolet and infrared degradation of the polymer core of an LCP may also improve the efficiency of an LCP so constructed by eliminating the need for polishing the end of an LCP which often leaves materials in the cladding that adversely affect the efficiency of the LCP.
Moreover, the novel methods herein disclosed may be practiced by a technician on-site to modify an existing system or in installation of new systems using known materials and instruments, thereby making the novel methods disclosed herein easy to adopt by the industry.
The methods disclosed in this application have the added advantage of being capable of implementation with very little cost and through the use of known and readily available materials, thus obviating the need to implement special manufacturing practices in the manufacturing of the LCPs themselves to produce ultraviolet and infrared resistive LCPs.
A typical device so constructed in accordance with this invention comprises an LCP which, through the modifications made possible by the methods disclosed herein, includes incorporated therein a glass member functioning to prevent the transmission of ultraviolet and infrared radiation to the polymer core. The glass member in such device may be further modified to provide other beneficial characteristics for the device itself.
Other objects will be in part obvious and in part pointed out more in detail hereinafter.